STEAM TURBINE AND METHOD FOR INTERNALLY COOLING THE SAME

Abstract

A steam turbine and a method for internally cooling the same. The steam turbine includes an outer casing and an inner casing; a rotor having a balancing piston, the rotor being rotatably mounted inside the inner casing; and a steam flow channel formed between the inner casing and the rotor. Moving blades fitted with the rotor and stationary blades fitted with the inner casing are alternately arranged to form multiple stages of blade groups, and an interlayer for steam to circulate is formed between the inner casing and the outer casing. The multiple stages of blade groups include a first set blade staging and a second set blade staging; and the top of the balancing piston is provided with a first chamber and a second chamber. A first channel disposed in the inner casing connects the flow passage downstream of the first set blade staging to the first chamber; and a second channel connects the second chamber to the interlayer and connects the interlayer to the flow passage downstream of the second set blade staging.

Claims

1. A steam turbine, comprising: an outer casing and an inner casing; a rotor having a balancing piston, the rotor being rotatably mounted inside the inner casing; and a steam flow channel formed between the inner casing and the rotor, wherein a plurality of moving blades fitted with the rotor and a plurality of stationary blades fitted with the inner casing are alternately arranged to form multiple stages of blade groups, and an interlayer for steam to circulate is formed between the inner casing and the outer casing; wherein: the multiple stages of blade groups include a first set blade staging and a second set blade staging; and the top of the balancing piston is provided with a first chamber and a second chamber; and a first channel disposed in the inner casing connects the flow passage downstream of the first set blade staging to the first chamber; and a second channel connects the second chamber to the interlayer and connects the interlayer to the flow passage downstream of the second set blade staging.

2. (canceled)

3. The steam turbine according to claim 1, wherein: the inner casing and the outer casing are provided with a live steam feed channel via which live steam is admitted into an inlet steam chamber; and the second chamber is disposed proximal to the inlet steam chamber, and the first chamber is disposed distant from the inlet steam chamber, the second chamber and the first chamber being arranged in a fore-and-aft manner along the axial direction of the rotor.

4. The steam turbine according to claim 3, wherein: a sideling placed stationary blade is provided for the inlet steam chamber in the inner casing upstream of the balancing piston, the pressure upstream of the balancing piston corresponding to the pressure downstream of the sideling placed stationary blade; or, the inlet steam chamber is free of the sideling placed stator, the pressure upstream of the balancing piston corresponding to the inlet pressure.

5. (canceled)

6. The steam turbine according to claim 1, wherein: a steam supplementing pipe extending through the outer casing is provided communicating with the interlayer between the inner casing and the outer casing or communicating with a steam supplementing chamber formed at the interlayer so as to introduce supplemental steam.

7. The steam turbine according to claim 4, wherein: the balancing piston is a single-diameter piston.

8. The steam turbine according to claim 4, wherein: the second set blade staging is disposed downstream of the first set blade staging in the flow channel and spaced from the first set blade staging by one or more blade stages; and the first set blade staging corresponds to the fourth blade stage or the fifth blade stage in the flow channel.

9. The steam turbine according to claim 1, wherein: the rotor is made of X12CrMoWVNbN10 or FB2 material.

10. A method for internally cooling a steam turbine, wherein the inner casing and the outer casing of the steam turbine are provided with a live steam feed channel to feed live steam into an inlet steam chamber within the inner casing, wherein the live steam starts from the inlet steam chamber into a flow channel between the inner casing and the rotor, and circulates around respective blade stage so as to be expanded and cooled, thereby releasing heat energy to drive the rotor to rotate; the method comprising: conveying, via a first channel in the inner casing, the steam from the flow passage downstream of a first designated blade staging in multiple stages of blade groups to a first chamber on the top of a balancing piston; and conveying, via a second channel, the steam from a second chamber on the top of the balancing piston till an interlayer between the inner casing and the outer casing, and then from the interlayer to the flow passage downstream of a second designated blade staging to continue working; or, conveying, via the first channel, the steam from the flow passage downstream of the first designated blade staging in the multiple stages of blade groups till the interlayer between the inner casing and the outer casing, and then from the interlayer to the first chamber on the top of the balancing piston; and conveying, via the second channel in the inner casing, the steam from the second chamber on the top of the balancing piston to a flow passage downstream of the second designated blade staging to continue working; wherein the pressure upstream of the balancing piston corresponds to the pressure downstream of the sideling placed stationary blade or corresponds to the inlet pressure.

11. A steam turbine, comprising: an outer casing and an inner casing; a rotor having a balancing piston, the rotor being rotatably mounted inside the inner casing; and a steam flow channel formed between the inner casing and the rotor, wherein a plurality of moving blades fitted with the rotor and a plurality of stationary blades fitted with the inner casing are alternately arranged to form multiple stages of blade groups, and an interlayer for steam to circulate is formed between the inner casing and the outer casing; wherein: the multiple stages of blade groups include a first set blade staging and a second set blade staging; and the top of the balancing piston is provided with a first chamber and a second chamber; and a first channel connects the flow passage downstream of the first set blade staging to the interlayer and connects the interlayer to the first chamber; and the second channel disposed in the inner casing connects the second chamber to the flow passage downstream of the second set blade staging; and a piston section of the balancing piston corresponding to the first chamber has the same diameter as a piston section corresponding to the second chamber.

12. The steam turbine according to claim 11, wherein: the inner casing and the outer casing are provided with a live steam feed channel via which live steam is admitted into an inlet steam chamber; and the second chamber is disposed proximal to the inlet steam chamber, and the first chamber is disposed distant from the inlet steam chamber, the second chamber and the first chamber being arranged in a fore-and-aft manner along the axial direction of the rotor.

13. The steam turbine according to claim 12, wherein: a sideling placed stationary blade is provided for the inlet steam chamber in the inner casing upstream of the balancing piston, the pressure upstream of the balancing piston corresponding to the pressure downstream of the sideling placed stationary blade; or, the inlet steam chamber is free of the sideling placed stator, the pressure upstream of the balancing piston corresponding to the inlet pressure.

14. The steam turbine according to claim 11, wherein: a steam supplementing pipe extending through the outer casing into the inner casing is provided communicating with the second channel or communicating with a steam supplementing chamber proximal to the second channel in the inner casing so as to introduce supplemental steam.

15. The steam turbine according to claim 13, wherein: the balancing piston is a single-diameter piston.

16. The steam turbine according to claim 13, wherein: the second set blade staging is disposed downstream of the first set blade staging in the flow channel and spaced from the first set blade staging by one or more blade stages; and the first set blade staging corresponds to the fourth blade stage or the fifth blade stage in the flow channel.

17. The steam turbine according to claim 11, wherein: the rotor is made of X12CrMoWVNbN10 or FB2 material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 shows a structural schematic diagram of a conventional steam turbine without internal cooling passages;

[0040] FIG. 2 shows a structural schematic diagram of a conventional steam turbine with two cooling passages;

[0041] FIG. 3 shows a structural schematic diagram of a steam turbine with a sideling placed stationary blade according to Embodiment 1 of the present disclosure;

[0042] FIG. 4 shows a structural schematic diagram of a steam turbine without a sideling placed stationary blade according to Embodiment 1 of the present disclosure;

[0043] FIG. 5 shows a structural schematic diagram of a steam turbine with a sideling placed stationary blade according to Embodiment 2 of the present disclosure; and

[0044] FIG. 6 shows a structural schematic diagram of a steam turbine without a sideling placed stationary blade according to Embodiment 2 of the present disclosure.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0045] Hereinafter, preferred embodiments of the present disclosure will be illustrated in further detail with reference to the accompanying drawings.

Embodiment I

[0046] As shown in FIG. 3, the steam turbine comprises an outer casing 110 and an inner casing 120, and a rotor 130 having a balancing piston 140, the rotor 130 being rotatably mounted inside the inner casing 120. A flow channel for a medium (e.g., steam) is formed between the inner casing 120 and the rotor 130, the flow channel substantially running along the axial direction of the rotor 130. The flow channel is alternately arranged with moving blades 150 fitted with the rotor 130 and stationary blades 160 fitted with the inner casing 120, forming multiple stages of blade groups. The inner casing 120 and the outer casing 110 are provided with a live stream feed channel (not shown) via which the live steam is admitted into the inlet steam chamber 170, where the live steam enters the flow channel and circulates downstream around respective blade stage; with expansion and cooling of the live steam, heat energy is released to drive the rotor 130 to rotate.

[0047] In this embodiment, with the first channel configured, the steam is enabled to flow into an interlayer 183 between the inner casing 120 and the outer casing 110 via a first connection pipe 182 in the inner casing 120 from the flow passage 181 downstream of one of the blade stages (referred to as the first blade staging) in the flow channel, and then from the interlayer 183, to flow into the first chamber 180 on the top of the balancing piston 140 via a second connecting pipe 184 in the inner casing 120.

[0048] In this embodiment, a second chamber 190 is further provided on the top of the balancing piston 140. The second chamber 190 is proximal to the inlet steam chamber 170, and the first chamber 180 is distant from the inlet steam chamber 170; the second chamber 190 and the first chamber 180 are arranged with a fore-and-aft spatial position relationship in the axial direction. The steam flows from the second chamber 190 into the flow passage 194 downstream of another one of the blade grades (referred to as the second blade staging) in the flow channel via the second channel arranged in the inner casing 120.

[0049] The first chamber 180 and the second chamber 190 may be a spatial structure of any shape, respectively formed in the inner casing 120 (or in some examples, formed at the balancing piston 140, or determined by respective shapes of the inner casing 120 and the balancing piston 140 at the interface therebetween).

[0050] In an exemplary first channel, the first connection pipe 182 extends upward within the inner casing 120 in a direction substantially perpendicular to the axis till accessing the interlayer 183, which is substantially parallel to the axis, between the inner casing 120 and the outer casing 110, and the second connection pipe 184 led out from the interlayer 183 further extends downward in the inner casing 120 in a direction substantially perpendicular to the axis till accessing the first chamber 180.

[0051] The exemplary second channel experiences two turns in the inner casing 120. In this example, a first pipe segment 191 led out from the second chamber 190 extends upward in a direction substantially perpendicular to the axis, and a second pipe segment 192 following the first turn extends in a direction substantially parallel to the axis, and a third pipe segment 193 following the second turn extends further downward in a direction substantially perpendicular to the axis till accessing the flow passage 194 downstream of the second blade staging.

[0052] Meanwhile, a steam supplementing pipe 100 extending through the outer casing 110 till accessing the inner casing 120 is provided communicating with the second channel (e.g., communicating with the third pipe segment 193 downstream of the second turn) or communicating with a steam supplementing chamber (not shown) disposed in the inner casing 120 adjacent to the third pipe segment 193, further conveying the introduced supplemental steam (schematically represented by the dotted-line arrow) to the flow passage 194 downstream of the second blade staging.

[0053] The second blade staging in the flow channel corresponding to the second chamber 190 is disposed downstream of the first blade staging corresponding to the first chamber 180, wherein the second blade staging and the first blade staging may be spaced by one or more stages of (e.g., two) blade groups. In this embodiment, the first blade staging is for example the fourth blade stage or the fifth blade stage.

[0054] In an alternative embodiment, the exemplary balancing piston 140 is a single-diameter piston.

[0055] In the example illustrated in FIG. 3, a sideling placed stationary blade 171 is provided in the inner casing 120 at the position corresponding to the inlet steam chamber 170 upstream of the balancing piston 140, i.e., the pressure upstream of the balancing piston 140 corresponds to the pressure downstream of the sideling placed stationary blade 171. The sideling placed stationary blade 171 is configurable to prevent the rotor 130 from being directly exposed to the steam, which can modestly lower the temperature of the rotor 130, so as to be beneficial to enhance strength of the rotor 130 or modestly raise the inlet parameters.

[0056] For example, the inlet steam has a temperature of 600° C. and a pressure of 27 MPa; downstream of the sideling placed stationary blade 171 has a temperature of 594° C. and a pressure of 26.3 MPa; downstream of the fourth blade stage has a temperature of 540° C. and a pressure of 18 MPa; downstream of the fifth stage blade has a temperature of 525° C. and a pressure of 16.5 MPa; the exhaust steam has a pressure of 6.5 MPa.

[0057] In another example illustrated in FIG. 4, the sideling placed stationary blade is absent upstream of the balancing piston 140, i.e., the pressure upstream of the balancing piston 140 corresponds to the inlet pressure.

Embodiment 2

[0058] As illustrated in FIG. 5, in the steam turbine according to this embodiment, the basic constructions of the outer casing 210, the inner casing 220, the rotor 230, the balancing piston 240, the first chamber 280, the second chamber 290, and the moving blades 250 and stationary blades 260 in multiple stages of blade groups are all identical to Embodiment 1. The main differential lies in the manner of arranging the first channel, the second channel, and the steam supplementing construction.

[0059] In this embodiment, the first channel is wholly provided within the inner casing 220, the input end of which communicates with a flow passage 281 downstream of the first blade staging in the flow channel running along the axial direction of the rotor 230, and the output end of which communicates with the first chamber 280 on the top of the balancing piston 240. With the second channel configured in this embodiment, the steam is admitted into the interlayer 292 between the inner casing 220 and the outer casing 210 from a second chamber 290 on the top of the balancing piston 240 via a first connection pipe 291, and is then conveyed to the flow passage 294 downstream of the second blade staging in the flow channel via a second connection pipe 293 connected to the interlayer 292.

[0060] In this embodiment, the second chamber 290 is proximal to the inlet steam chamber 270, and the first chamber 280 is distant from the inlet steam chamber 270; the second chamber 290 and the first chamber 280 are arranged with a fore-and-aft spatial position relationship in the axial direction. The second blade staging corresponding to the second chamber 290 is disposed downstream of the first blade staging corresponding to the first chamber 280; the second blade staging and the first blade staging may be spaced by one or more stages (e.g., two stages) of blade groups. The first blade staging is for example the fourth blade stage or the fifth blade stage.

[0061] The exemplary first channel experiences two turns in the inner casing 220. In this example, a first pipe segment 282 led out from the flow passage downstream of the second blade staging extends upward in a direction substantially perpendicular to the axis, and a second pipe segment 283 following the first turn extends in a direction substantially parallel to the axis, and a third pipe segment 284 following the second turn extends further downward in a direction substantially perpendicular to the axis till accessing the first chamber 280.

[0062] In an exemplary second channel, the first connection pipe 291 led out from the second chamber 290 extends upward within the inner casing 220 in a direction substantially perpendicular to the axis till accessing the front segment of the interlayer 292, which is substantially parallel to the axis, between the inner casing 220 and the outer casing 210, and then the second connection pipe 293 is led out from a certain position at the rear segment of the interlayer 292, the second connection pipe 293 extending downward in the inner casing 220 in the direction substantially perpendicular to the axis till accessing the flow passage 294 downstream of the first blade staging.

[0063] In an alternative embodiment, the exemplary balancing piston 240 is a single-diameter piston.

[0064] In the example illustrated in FIG. 5, a sideling placed stationary blade 271 is provided in the inner casing 220 at the position corresponding to the inlet steam chamber 270 upstream of the balancing piston 240, i.e., the pressure upstream of the balancing piston 240 corresponds to the pressure downstream of the sideling placed stationary blade 271. In another example illustrated in FIG. 6, the sideling placed stationary blade is absent upstream of the balancing piston 240, i.e., the pressure upstream of the balancing piston 240 corresponds to the inlet pressure.

[0065] The steam supplementing pipe 220 in this embodiment, after extending through the outer casing 210, accesses the interlayer 292 between the inner casing 220 and the outer casing 210 to introduce supplemental steam to be mixed with the steam that accesses the interlayer 292 from the second chamber 290. The access position of the steam supplementing pipe 200 in the region of the interlayer is not limited, wherein the steam supplementing pipe 200 is movable fore-and-aft along the axial direction.

[0066] Illustratively, a steam supplementing chamber surrounding the outer side of the inner casing 220 may be provided in the region of the interlayer between the inner casing 220 and the outer casing 210. The steam supplementing chamber may be a spatial structure of any shape, defined by respective body shapes of the outer casing 210 and the inner casing 220 at the position where the steam supplementing chamber is provided. For example, the steam supplementing chamber is an annular chamber.

[0067] In view of the above, a steam turbine and a method of internally cooling the same are provided, wherein by providing two cooling passages within the steam turbine, the first chamber and the second chamber on the top of the balancing piston are respectively connected to the flow channels downstream of their corresponding blade stages, which simplifies the cooling loop while guaranteeing qualified strength and safety, thereby achieving the objectives of reducing rotor diameter, lowering costs, and simplifying casing structures.

[0068] Although the contents of the present disclosure have been described in detail through the foregoing preferred embodiments, it should be understood that the depictions above shall not be regarded as limitations to the present disclosure. After those skilled in the art having read the contents above, many modifications and substitutions to the present disclosure are all obvious. Therefore, the protection scope of the present disclosure should be limited by the appended claims.